标题： 被遮蔽与未被遮蔽的活动星系核演化与X射线背景 显示英文标题

标题： Obscured and Unobscured AGN Evolution and the X-ray background

摘要： 大天文台起源深空巡天（GOODS）结合了哈勃太空望远镜（HST）和斯皮策（Spitzer）的深度成像与最深的钱德拉（Chandra）/欧空局XMM观测，以探测比以往多波段巡天更高的红移处被遮蔽的活动星系核（AGN）。我们提出了一种自洽的活动星系核统一范式实施方法，该范式假设在有未遮蔽AGN的地方也存在被遮蔽的AGN，成功解释了在GOODS区域探测到的X射线源的红外、光学和X射线数目计数。假定遮蔽与未遮蔽AGN的比例为3:1（即局部值），或者该比例随光度降低，并且包括康普顿厚源，我们可以解释星系际X射线“背景”的谱形和归一化，这主要由z~0.5-1.5、L_x~10^43-10^44 ergs/s范围内的未分辨AGN叠加而成。遮蔽与未遮蔽AGN比例随红移变化的可能依赖性尚未得到良好约束；现有数据允许它在z~1以上大幅下降或上升。 显示英文摘要

摘要： The Great Observatories Origins Deep Survey (GOODS) combines deep HST and Spitzer imaging with the deepest Chandra/XMM observations to probe obscured AGN at higher redshifts than previous multiwavelength surveys. We present a self-consistent implementation of the AGN unification paradigm, which postulates obscured AGN wherever there are unobscured AGN, to successfully explain the infrared, optical, and X-ray number counts of X-ray sources detected in the GOODS fields. Assuming either a constant ratio of obscured to unobscured AGN of 3:1 (the local value), or a ratio that decreases with luminosity, and including Compton-thick sources, we can explain the spectral shape and normalization of the extragalactic X-ray "background" as a superposition of unresolved AGN, predominantly at z~0.5-1.5 and L_x~10^43-10^44 ergs/s. The possible dependence of the obscured to unobscured ratio with redshift is not well constrained; present data allow it to decrease or increase substantially beyond z~1.